A new report suggests the Environmental Protection Agency should consider lowering the legal limit in drinking water for nitrates, a chemical often connected to fertilizer use.

People who drink water with elevated, but not illegal, levels of nitrates could be at an increased risk of kidney, ovarian and bladder cancer, the nonprofit Environmental Working Group asserts. But a University of Iowa researcher who studies nitrate contamination says the connection to cancer is inconsistent and other chemicals may be involved.

After court documents unsealed Tuesday raised questions about its research methods, chemical giant Monsanto said it did not ghostwrite a 2000 study on the safety of glyphosate, the active ingredient in its flagship pesticide Roundup.

After dueling reviews of research studies, scientific panels from the U.S. government and the World Health Organization are having a hard time agreeing whether glyphosate, the most common weed killer in the United States, can cause cancer. Known by the brand name RoundUp, glyphosate is sprayed on farm fields and lawns all across the country.

Just over a year ago, Tracy Dethlefs learned she has stage 1 breast cancer. Since then, she estimates she has charted some 10,000 miles traveling from her farm near Loup City in central Nebraska to area hospitals for treatment. Every surgery, round of chemotherapy and radiation treatment was a road trip.